Pharmaceuticals and cosmetics are high technology products which require very specialized material systems and production procedures as well as very large investments in development and marketing. Because of public safety concerns, authorities place very stringent requirements on the verification and authenticity of such products. Companies therefore have to make huge investments in the tracking and tracing of these products to ensure authenticity. In addition, as these products usually have large sales margins and are distributed globally, it is not surprising that cosmetics manufacturers and pharmaceutical companies suffer from enormous losses due to counterfeiting. The problem has been aggravated by strongly increased sales over the internet, where everything from counterfeit Viagra to false glucose tests is readily available.
Track-and-trace features in the pharmaceutical market have been applied to packages. For example, holograms, optically variable inks, fluorescent dyes, and other identification features are attached to the packages, e.g., by adhesive tags. Alternatively, such labels are laminated to the carton or are directly applied to the packages. The main drawback of such labels is that they are not an integral part of the tablet and therefore do not provide 100% security. For example, if the authentic product is separated from the package, the package can be refilled with a false product. Therefore, direct verification of an authentic tablet, and ensuring that the authentic tablet is in the correct package, remains a primary concern.
Although there are some known approaches for secure labelling of the tablets themselves, each suffers from one or more drawbacks.
For instance, techniques based on forgery-resistant signatures, such as DNA of known sequence (U.S. Pat. No. 5,451,505) or molecules with characteristic isotopic composition or micro-particles with characteristic colour layer sequence (U.S. Pat. No. 6,455,157 B1), are considered unsuitable for pharmaceutical tablets, as these signatures are administered simultaneously and require additional regulatory approval.
WO2006/027688A1 describes an article, such as a tablet, having a visible diffractive microstructure on its surface or at an interface. Illuminated with white light, the tablet shows a rainbow colour effect similar to holograms. The diffractive microstructure can provide an indication of authenticity of the tablet. Although suitable for verification purposes, that document discloses a security element that is visible to the unaided eye. This visibility can tip off counterfeiters. Second, it is difficult to encode a large amount of data in such diffractive microstructures, and to do so consistently.
EP1958620A1 teaches a verification method based on three-dimensional structures such as barcodes or logos impressed or embossed in tablets, in particularly pharmaceutical tablets. Further methods to manufacture tablet compression tools are disclosed. This patent application is incorporated in its entirety.
A number of optical detection devices useful for analysing three-dimensional structures are known. White light interferometers are state of the art but operate rather slowly. Optical coherence tomography (OCT) is another known technique capable of visualising three dimensional patterns, even if they are located at an interface below the surface of an article. The depth that can be visualised in a material depends on the optical properties of the material. It can be up to a few millimetres at present. U.S. Pat. No. 6,469,489 describes an array sensor which is used for parallel optical low-coherence tomography (pOCT) which enables real-time 3D imaging for topographic pattern. It provides fast, three-dimensional and structural information with spatial resolution in the micrometer range. A plurality of electrical detection circuits with parallel outputs can form a one-dimensional or two-dimensional array sensor for the coherent or heterodyne analogue detection of intensity modulated optical signals simultaneously for all pixels with a high dynamic range. The array sensor may be used, e.g., for optical 3D measurements, and especially in optical low-coherence tomography. It is known to use OCT for investigating the human skin, to control the quality of fast production processes (e.g., in die-bonding), in SMD pick-and-place systems, as well as in mechanical inspection systems. Variants of these detection techniques do not use interferometry, but time-modulated optical signals to provide accurate 3D measurements of objects. Such variants often use parallel processing of lock-in signals on a single chip to provide fast and accurate distance information to an object. One example is time-of-flight (TOF) or related methods, where infrared or visible light from a camera's internal lighting source is time modulated and reflected by objects in the scene. It travels back to the camera, where its time of arrival is measured independently by each pixel on a sensor array or chip. In contrast to conventional cameras, such cameras provide a complete distance map of all objects in the field of view on a pixel-by-pixel basis.